SEC Petition Evaluation Report

Petition SEC-00218

Report Rev #:0 Report Submittal Date: July 17, 2014

Subject Expert(s): Toshihide Ushino

Site Expert(s): N/A

Petitioner Administrative Summary

Petition Under Evaluation

Petition # Petition 

Type

Petition A

Receipt Date DOE/AWE Facility Name

SEC-00218 83.14 June 27, 2014 General Atomics

NIOSH-Proposed Class Definition

All Atomic Weapons Employees who worked for General Atomics at its facility in La Jolla, 

California, during the period from January 1, 1960 through December 31, 1969, for a number of work 

days aggregating at least 250 work days, occurring either solely under this employment or in 

combination with work days within the parameters established for one or more other classes of 

employees included in the Special Exposure Cohort.

Related Petition Summary Information

SEC Petition 

Tracking #(s)

Petition 

Type DOE/AWE Facility Name Petition Status

SEC-00064 83.14 General Atomics Class added to the SEC for the period 

January 1, 1960 through December 31, 

1969 (Building Specific)

Related Evaluation Report Information

Report Title DOE/AWE Facility Name

SEC Petition Evaluation Report for Petition SEC-00064 General Atomics

ORAU Lead Technical Evaluator:

-Toshihide Ushino

ORAU Peer Review Completed By:

-Michael Kubiak

Peer Review Completed By: [Signature on File] 7/17/2014

LaVon Rutherford Date

SEC Petition Evaluation Reviewed By: [Signature on File] 7/17/2014

J. W. Neton Date

SEC Evaluation Approved By: [Signature on File] 7/17/2014

Stuart L Hinnefeld Date
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Evaluation Report Summary: SEC-00218, General Atomics

This evaluation report by the National Institute for Occupational Safety and Health (NIOSH) 

addresses a class of employees proposed for addition to the Special Exposure Cohort (SEC) per the 

Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 42 U.S.C. 

§ 7384 et seq. (EEOICPA) and 42 C.F.R. pt. 83, Procedures for Designating Classes of Employees 

as Members of the Special Exposure Cohort Under the Energy Employees Occupational Illness 

Compensation Program Act of 2000.

NIOSH-Proposed Class Definition

The intent of this evaluation is to address consistency and implementation issues associated with

NIOSH’s 2006 Special Exposure Cohort Evaluation for General Atomics, specifically SEC-00064

(NIOSH, 2006). A NIOSH review of existing SEC class definitions evaluated criteria such as 

consistency, applicability, and whether any class definitions needed to be corrected by NIOSH 

(DCAS, 2010). In this review, NIOSH determined that the class definition as set forth in SEC-00064 

needed revising because of the potential for difficulties in implementing the class definition. In 

addition, through the course of ongoing dose reconstruction and research, NIOSH has determined that, 

due to undocumented worker movements across the site, limited claimant-specific information 

pertaining to work locations, and observation that that employment records do not always indicate 

work locations, NIOSH is unable to eliminate any specific worker from potential exposure scenarios 

based on assigned work location. NIOSH has found that a determination cannot always be made as to 

the specific area an employee worked in, or whether an employee should have been monitored for 

radiological exposures.

Accordingly, NIOSH has determined that it is necessary to remove the area-specific and monitoring 

criteria from the class description associated with SEC-00064 for the period from January 1, 1960 

through December 31, 1969. As such, NIOSH recommends expanding the SEC class definition to 

include all areas of the General Atomics facility, and to include all Atomic Weapons Employees who 

worked for General Atomics during the period from January 1, 1960 through December 31, 1969. 

This SEC-00218 evaluation recommends a class that is consistent with current NIOSH methods for 

defining a recommended SEC class. 

The NIOSH-proposed class definition is all Atomic Weapons Employees who worked for General 

Atomics at its facility in La Jolla, California, during the period from January 1, 1960 through 

December 31, 1969, for a number of work days aggregating at least 250 work days, occurring either 

solely under this employment or in combination with work days within the parameters established for 

one or more other classes of employees included in the Special Exposure Cohort.

Feasibility of Dose Reconstruction Findings

NIOSH lacks sufficient information, which includes biological monitoring data, sufficient air 

monitoring information, or sufficient process and radiological source information, that would allow it 

to estimate with sufficient accuracy the potential unmonitored internal exposures, including 

unmonitored uranium, thorium, plutonium, tritium, and fission and activation products, to which the 

proposed class may have been subjected during the period from January 1, 1960 through December 
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31, 1969. Although NIOSH found that it is not possible to completely reconstruct radiation doses for 

the proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). 

The NIOSH dose reconstruction feasibility findings are based on the following:

• Principal sources of internal radiation for members of the proposed class included exposures to 

uranium isotopes (depleted, natural, enriched and recycled), plutonium, thorium, tritium, and other 

fission and activation products associated with radiological research and production activities, 

including reactor and accelerator operations.

• NIOSH has determined that it is necessary to remove the area-specific and monitoring criteria 

from the class description associated with NIOSH’s 2006 evaluation of SEC-00064 exposures for 

the period from January 1, 1960 through December 31, 1969. Additionally, due to the issues 

identified during ongoing dose reconstruction and methodology reviews conducted by NIOSH and 

the Advisory Board on Radiation and Worker Health (the Board) after implementation of SEC00064, NIOSH has determined that infeasibilities associated with sufficiently accurate 

reconstruction of internal exposures during that period extend beyond the assessment of thorium 

exposures as was presented in NIOSH’s 2006 evaluation of General Atomics. NIOSH lacks 

sufficient information that would allow it to estimate with sufficient accuracy the potential 

unmonitored internal exposures, including unmonitored uranium, thorium, tritium, and fission and 

activation products, to which the proposed class may have been subjected during the period from 

January 1, 1060 through December 31, 1969. 

• Principal sources of external radiation for members of the proposed class included exposures to 

radiation fields associated with reactor, accelerator, and fuel production operations and 

experiments.

• Through the course of ongoing dose reconstruction and methodology reviews conducted by 

NIOSH and the Board after implementation of SEC-00064, NIOSH has also determined that 

NIOSH is unable to define individual worker external exposure scenarios for those workers that 

were not monitored for external exposure. NIOSH does not have access to sufficient personnel 

monitoring, workplace monitoring, or source term data to estimate unmonitored external beta, 

gamma, or neutron exposures during the period from January 1, 1960 through December 31, 1969.

• NIOSH considers that sufficiently accurate reconstruction of medical dose for General Atomics 

workers is feasible by using claimant-favorable assumptions as well as applicable protocols 

specified in the complex-wide ORAUT-OTIB-0006, Technical Information Bulletin: Dose 

Reconstruction from Occupationally Related Diagnostic X-Ray Procedures.

• Pursuant to 42 C.F.R. § 83.13(c)(1), NIOSH determined that there is insufficient information to 

either: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred under plausible circumstances by any 

member of the class; or (2) estimate the radiation doses of members of the class more precisely 

than a maximum dose estimate.
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Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for individuals employed at 

General Atomics during the period from January 1, 1960 through December 31, 1969, but who do not 

qualify for inclusion in the SEC, may be performed using these data as appropriate.

Health Endangerment Determination

The NIOSH evaluation did not identify any evidence supplied by the petitioners or from other 

resources that would establish that the class was exposed to radiation during a discrete incident likely 

to have involved exceptionally high-level exposures, such as nuclear criticality incidents or other 

events involving similarly high levels of exposures. However, the evidence reviewed in this 

evaluation indicates that some workers in the class may have accumulated chronic radiation exposures 

from radionuclides of uranium, thorium, plutonium, tritium, and fission and activation products 

associated with radiological research and production activities, including reactor and accelerator 

operations. Therefore, 42 C.F.R. § 83.13(c)(3)(ii) requires NIOSH to specify that health may have 

been endangered for those workers covered by this evaluation who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for this class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC.
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Table of Contents

Evaluation Report Summary: SEC-00218, General Atomics ................................................................. 3

1.0 Purpose and Scope....................................................................................................................... 9

2.0 Introduction ................................................................................................................................. 9

3.0 NIOSH-Proposed Class Definition and Petition Basis.............................................................. 10

4.0 Radiological Operations Relevant to the Proposed Class ......................................................... 11

4.1 Operations Description..................................................................................................... 11

4.2 Radiation Exposure Potential from Operations................................................................ 16

4.3 Time Period Associated with Radiological Operations.................................................... 18

4.4 Site Locations Associated with Radiological Operations ................................................ 18

4.5 Job Descriptions Affected by Radiological Operations ................................................... 19

5.0 Summary of Available Monitoring Data for the Proposed Class.............................................. 19

5.1 Data Capture Efforts and Sources Reviewed ................................................................... 19

5.2 Previous Dose Reconstructions........................................................................................ 20

5.3 Worker Interviews............................................................................................................ 20

5.4 Internal Personnel Monitoring Data ................................................................................. 20

5.5 External Personnel Monitoring Data ................................................................................ 22

5.6 Workplace Monitoring Data............................................................................................. 23

5.7 Radiological Source Term Data ....................................................................................... 23

6.0 Feasibility of Dose Reconstruction for the Proposed Class ...................................................... 25

6.1 Feasibility of Estimating Internal Exposures ................................................................... 25

6.2 Feasibility of Estimating External Exposures .................................................................. 30

6.3 Class Parameters Associated with Infeasibility................................................................ 32

7.0 Summary of Feasibility Findings for Petition SEC-00218........................................................ 32

8.0 Evaluation of Health Endangerment for Petition SEC-00218................................................... 34

9.0 NIOSH-Proposed Class for Petition SEC-00218 ...................................................................... 34

10.0 Evaluation of Second Similar Class.......................................................................................... 34

11.0 References ................................................................................................................................. 35

Attachment One: Data Capture Synopsis.............................................................................................. 39
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Tables

Table 4-1: General Atomics Facilities that Conducted Radiological Work.......................................... 13

Table 5-1: No. of Site Name Claims Submitted Under the Dose Reconstruction Rule........................ 20

Table 5-2: Allowable Quantities of Radioactive Material at General Atomics .................................... 24

Table 7-1: Summary of Feasibility Findings for General Atomics....................................................... 33
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SEC Petition Evaluation Report for SEC-00218

ATTRIBUTION AND ANNOTATION: This is a single-author document. All conclusions drawn from 

the data presented in this evaluation were made by the ORAU Team Lead Technical Evaluator: 

Toshihide Ushino, MJW Corporation. The rationales for all conclusions in this document are 

explained in the associated text.

1.0 Purpose and Scope

This report evaluates the feasibility of reconstructing doses for employees who worked at General 

Atomics during a specified time. It provides information and analysis germane to considering a 

petition for adding a class of employees to the Congressionally-created SEC.

This report does not make any determinations concerning the feasibility of dose reconstruction that 

necessarily apply to any individual energy employee who might require a dose reconstruction from 

NIOSH, with the exception of the employee whose dose reconstruction could not be completed, and 

whose claim consequently led to this petition evaluation. The finding in this report is not the final 

determination as to whether or not the proposed class will be added to the SEC. This report will be 

considered by the Advisory Board on Radiation and Worker Health (the Board) and by the Secretary 

of Health and Human Services (HHS). The Secretary of HHS will make final decisions concerning 

whether or not to add one or more classes to the SEC in response to the petition addressed by this 

report.

This evaluation, in which NIOSH provides its findings both on the feasibility of estimating radiation 

doses of members of this class with sufficient accuracy and on health endangerment, was conducted in 

accordance with the requirements of EEOICPA and 42 C.F.R. § 83.14.

2.0 Introduction

Both EEOICPA and 42 C.F.R. pt. 83 require NIOSH to evaluate qualified petitions requesting that the 

Department of Health and Human Services add a class of employees to the SEC. The evaluation is 

intended to provide a fair, science-based determination of whether it is feasible to estimate, with 

sufficient accuracy, the radiation doses of the proposed class of employees through NIOSH dose 

reconstructions.

1

NIOSH is required to document its evaluation in a report, and to do so, relies upon both its own dose 

reconstruction expertise as well as technical support from its contractor, Oak Ridge Associated 

Universities (ORAU). Once completed, NIOSH provides the report to both the petitioners and the 

Advisory Board on Radiation and Worker Health. The Board will consider the NIOSH evaluation 

report, together with the petition, comments of the petitioner(s) and such other information as the 

Board considers appropriate, to make recommendations to the Secretary of HHS on whether or not to 

add one or more classes of employees to the SEC. Once NIOSH has received and considered the 

advice of the Board, the Director of NIOSH will propose a decision on behalf of HHS. The Secretary 

 1 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available at http://www.cdc.gov/niosh/ocas.
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of HHS will make the final decision, taking into account the NIOSH evaluation, the advice of the 

Board, and the proposed decision issued by NIOSH. As part of this final decision process, the 

petitioner(s) may seek a review of certain types of final decisions issued by the Secretary of HHS.

2

3.0 NIOSH-Proposed Class Definition and Petition Basis

The NIOSH-proposed class includes all Atomic Weapons Employees who worked for General 

Atomics at its facility in La Jolla, California, during the period from January 1, 1960 through 

December 31, 1969, for a number of work days aggregating at least 250 work days, occurring either 

solely under this employment or in combination with work days within the parameters established for 

one or more other classes of employees included in the Special Exposure Cohort. During this period, 

employees at this facility performed an array of radiological research and production activities to 

support development of commercial applications for nuclear technology.

The evaluation responds to Petition SEC-00218 which was submitted by an EEOICPA claimant 

whose dose reconstruction could not be completed by NIOSH due to a lack of sufficient dosimetryrelated information. NIOSH’s determination that it is unable to complete a dose reconstruction for an

EEOICPA claimant is a qualified basis for submitting an SEC petition pursuant to 42 C.F.R. § 

83.9(b).

There is currently one class of General Atomics workers associated with the previous NIOSH 

evaluation of SEC petition SEC-00064 (NIOSH, 2006), for which the Secretary of HHS has 

designated inclusion in the Special Exposure Cohort:

Class added to the SEC effective March 18, 2007: All AWE employees who were monitored or 

should have been monitored for exposure to ionizing radiation while working at the following 

General Atomics locations: Science Laboratories A, B, and C (Building 2); Experimental Building 

(Building 9); Maintenance (Building 10); Service Building (Building 11); Buildings 21 and 22; 

Hot Cell Facility (Building 23); Waste Yard (Buildings 25 and 26); Experimental Area (Buildings 

27 and 27-1); LINAC Complex (Building 30); HTGR-TCF (Building 31); Fusion Building 

(Building 33); Fusion Doublet III (Building 34); SV-A (Building 37); SV-B (Building 39); and 

SV-D (no building number) for a number of work days aggregating at least 250 work days from 

January 1, 1960, through December 31, 1969, or in combination with work days within the 

parameters established for one or more other classes of employees in the SEC.

A NIOSH review of existing SEC class definitions evaluated criteria such as consistency, 

applicability, and whether any class definitions needed to be corrected by NIOSH (DCAS, 2010). In 

this review, NIOSH determined that the class definition as set forth in SEC-00064 needed revising

because of the potential for difficulties in implementing the class definition. In addition, through the 

course of ongoing dose reconstruction and research, NIOSH has determined that, due to 

undocumented worker movements across the site, limited claimant-specific information pertaining to 

work locations, and observation that that employment records do not always indicate work locations, 

NIOSH is unable to eliminate any specific worker from potential exposure scenarios based on 

assigned work location. NIOSH has found that a determination cannot always be made as to the 

 2 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available at http://www.cdc.gov/niosh/ocas.
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specific area an employee worked in, or whether an employee should have been monitored for 

radiological exposures.

Accordingly, NIOSH has determined that it is necessary to remove the area-specific and monitoring 

criteria from the class description associated with SEC-00064 for the period from January 1, 1960 

through December 31, 1969. As such, NIOSH recommends expanding the SEC class definition to 

include all areas of the General Atomics facility, and to include all Atomic Weapons Employees who 

worked for General Atomics during the period from January 1, 1960 through December 31, 1969. 

This SEC-00218 evaluation recommends a class that is consistent with current NIOSH methods for 

defining a recommended SEC class.

4.0 Radiological Operations Relevant to the Proposed Class 

The following subsections summarize the radiological operations at General Atomics from January 1, 

1960 through December 31, 1969, and the information available to NIOSH to characterize particular 

processes and radioactive source materials. Using available sources, NIOSH has attempted to gather 

process and source descriptions, information regarding the identity and quantities of radionuclides of 

concern, and information describing processes through which the radiation exposures of concern may 

have occurred and the physical environment in which they may have occurred. The information 

included within this evaluation report is meant only to be a summary of the available information.

4.1 Operations Description

General Atomics is located in La Jolla, California, on 60-acres on the Torrey Pines Mesa site. The 

main site is approximately 300-feet above sea level, 1-mile from the Pacific Ocean, and 13-miles 

northwest of downtown San Diego. The General Atomics site is in the center of the Torrey Mesa 

Science Center, a 304-acre industrial park. The majority of General Atomics buildings are on top of 

the mesa, but some work, such as work at the Fuel Fabrication Facility (Building 37) and the Fusion 

Energy Facility (also known as DIII-D National Fusion Facility), occurred (and some still occurs) at 

the base of the mesa to the east of the central set of site buildings. For the period evaluated by 

NIOSH, the General Atomics workforce consisted of approximately 1,900 workers. Of the 

approximately 1,900 workers (obtained by averaging data from 1960 through 1964), approximately 

400 workers/year were monitored for external penetrating doses.

General Dynamics Corporation established the General Atomics Division in San Diego, California, to 

develop commercial applications for nuclear technology. General Atomics performed an array of 

radiological research and production activities at its Torrey Pines Mesa facility in La Jolla, California 

(General Atomics, 1998). General Atomics operated under licenses first issued by the Atomic Energy 

Commission (AEC) and later by the State of California. The General Atomics source term includes 

depleted, normal, and highly-enriched uranium [typically greater than 20% and up to 93.5% (SNM696) U-235 by mass]. This uranium was in the form of scrap, fresh reactor fuel, and irradiated reactor 

fuel comprised of uranium, activation products, and fission products. Thorium was used in fuel 

fabrication work. Plutonium work was also done on site. Four linear accelerators (LINACs) and 

several nuclear reactors were employed. Sealed sources were used for instrument calibrations and 

other work. By-product materials (Atomic Numbers 3-83) and tritium were also used. 

General Atomics performed irradiation and time-of-flight studies with four LINACs; developed and 
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fabricated reactor fuels; operated three on-site TRIGA reactors (Training/Research/Isotopes General 

Atomics); performed fusion research (since the mid-1960s); ran experimental criticality test facilities; 

used an “experimental” facility that is understood to have conducted a diverse set of tests with 

radioactive materials; and worked with special nuclear material (SNM) and radioactive tracers in its 

laboratory facilities. Hot Cells were used for handling radioactive materials associated with high 

radiation fields or very large quantities of radioactive materials that might be subject to processes 

resulting in dispersion. Operations conducted in these hot cells included post-irradiation examinations 

of DOE fuels, structural materials, and reactor dosimetry materials; and mechanical inspection of 

irradiated fuel. Development and manufacture of Experimental Beryllium Oxide Reactor (EBOR) 

fuel, tritium extraction, and experiments to test plutonium transport using plutonium oxide were also 

performed in hot cells. 

Fuel fabrication involved working with uranium (up to 93.5% U-235 by mass) and thorium. 

Radioactive materials were coated, blended, compounded, heated, rolled, extruded, machined, 

compacted, and eventually made into fuel elements. There were many tasks required for fuel 

fabrication whereby raw materials were converted to usable fuel assemblies. 

General Atomics reclaimed highly-enriched uranium (HEU) from non-irradiated NERVA (Nuclear 

Engines for Rocket Vehicle Applications) scrap fuel. The scrap was identified as being in Scrap 

Groups III (uranium compounds such as oxides) and IV (combustibles such as paper, tissue wipes, 

filters, etc.). The scrap materials were to be shipped from the Westinghouse Electric Corporation’s 

Astrofuel Facility in Cheswick, Pennsylvania, to General Atomics for processing into uranium oxides 

(Type III recovered uranium: UO2, UO3, and U3O8). SNM in the form of uranium-bearing impure 

scrap materials (e.g., oxides or carbides) was processed to recover and purify the contained uranium. 

The material was accumulated from several sources (both on-site and off-site), including out-ofspecification SNM product, process equipment, scrap, waste, and solid residue from liquid 

evaporation. Some of the materials came from the facility recovery operations. 

The steps used for uranium material extraction and purification are described in SNM License 696 

(SNM-96). In addition to the production, research, and recovery activities conducted with uranium 

and SNM, General Atomics also worked with thorium materials. Thorium was one of the 

radionuclides used in the initial stages of operation; such use continued through the operational 

period. Thorium was used in Building 2 (Science Laboratories) for testing mixtures and components 

of fuel assemblies. The thorium operations conducted in Building 2 included grinding of thorium, 

high-temperature heating under vacuum, and fabrication of thorium-uranium gel. Undetermined 

amounts of thorium were used in Building 9 (Experimental Building); operations included extrusion, 

rolling, cutting, milling, lathing, and casting of metal. Research and development of reactor fuel 

pellets using uranium and thorium was one of the activities conducted in Building 23 (Hot Cell 

Facility). When work was performed in hot cells, there was the potential for exposure during the 

transport of radioactive materials to and from the Hot Cells and during maintenance of equipment. 

Radioactive materials containing thorium and other radionuclides were volume-reduced at, stored at, 

and shipped from the Waste Yard (Buildings 25 and 26). Information regarding the total quantities 

and activities of individual radionuclides handled at the Waste Yard has not been identified.

Coated thorium fuel pellets were irradiated in the linear accelerator building (LINAC Complex or 

Building 30). Other research activities involving thorium were also conducted at the LINAC 

Complex. Criticality testing of fuel elements containing thorium was routinely conducted at the 
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Critical Assembly Facility (Building 31); thorium compaction also occurred in this facility. 

Fabrication and testing of HTGR (High Temperature Gas Cooled Reactor) fuel was performed in 

Buildings 37 (SV-A) and 39 (SV-B). One of the primary uses of thorium at General Atomics was in 

the fabrication of Th-U fuel. Potential exposure to thorium in these Sorrento Valley areas resulted in 

part from the transport and handling of materials, maintenance of fabrication equipment, and 

airborne leaks from the thorium conversion furnace (SNM-696). 

Records suggest that thorium was routinely used in the aforementioned buildings. However, based on 

available documentation (General Atomics, 1964; SNM-696), the transfer, storage, and use of thorium 

in other radiological buildings was also likely. NIOSH has not located documentation on the amount 

of thorium used and processes employed in these remaining buildings or on the level of thorium 

activity in any specific locations of the facility.

Table 4-1: General Atomics Facilities that Conducted Radiological Work

Building Process

Building 2 Science Laboratories A, B, and C* Radiological and chemical laboratories 

Building 9 Experimental Building (E Building)* Many radiological operations, including fuel element 

development and Pu storage 

Building 10 Maintenance Building Radioanalytical laboratory and Health Physics 

Building 11 Service Building Shipping and receiving of radioactive materials 

Building 21 (TRIGA) Housed three TRIGA reactors 

Building 22 TRIGA Fuel Fabrication 

Building 23 (Hot Cell Facility)* Multiple radiological operations 

Buildings 25* and 26 * Waste handling, minimization, processing, and storage; 

SNM storage; and a gamma counting facility 

Building 27 (Experimental Area Building #1) Preparation of target samples for neutron irradiation; postirradiation radiochemical separations 

Building 27-1 (Experimental Area Building #1 – Bunker; 

also contained ‘Strontium Facility’) 

Neutron activation; yttrium production from Sr-90; and 

research and development 

Building 30 (LINAC Complex)* High-energy electron accelerators 

Building 31 (HTGR-TCF)* Also called the Critical 

Assembly Facility 

Testing of fuel elements 

Building 33 (Fusion Building) Study of controlled thermonuclear reactions 

Building 34 (Fusion Doublet III) Research in magnetic fusion technologies (involving shortlived radiation sources) 

Building 37 (SV-A)* Fabrication of fuel elements; SNM 

Building 39 (SV-B)* Fabrication and testing of fuel assemblies for HTGR; SNM 

SV-D (no building number) Assembled thermionic and thermoelectric fuel elements; 

SNM 

Note:

* Records suggest that thorium was routinely used in these buildings. However, based on available documentation 

(General Atomics, 1964; SNM-696) the transfer, storage, and use of thorium in other radiological buildings was also 

likely.

Some of the larger radiological operations involved the Fuel Fabrication Facility, the Hot Cell Facility 

(Building 23), the reactors, and the linear accelerator. In addition, there were a number of research 

and development and small-scale manufacturing projects on going in the General Atomics research 

and experimental buildings. Although many of the facilities were operational by 1960, some were 

moved or constructed during the 1960s. This evaluation report identifies the functional areas and 

facilities where thorium was handled, used, or processed. A list of these facilities is shown in Table 4-

1; these thorium facilities are discussed in the successive report sub-sections.
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LINAC Facility

The LINAC facility began operating in 1962 and was used for a variety of research activities. Early 

experiments investigated the intensity of delayed radiations from the fission of uranium-238, 

uranium-235, plutonium-239, and thorium-232 (General Atomics, 1964). Tritium was also used as 

a LINAC target. However, information on the design and construction of the targets was not found.

Administrative controls coupled with physical interlocks were used to ensure the safety and protection 

of LINAC personnel. Any material registering over twice background on an alpha, beta, or gamma 

detector was considered radioactive (SNM-69).

Experimental Building (E Building)

The Experimental Building was involved in much of the initial fuel development work conducted 

onsite. The first major operation conducted within the facility was the fabrication of TRIGA reactor 

fuel elements (UZrH, a uranium-zirconium hydride alloy). There were two radiologically-controlled 

areas within the structure, designated as Zones A (South Control Zone: A-1, A-2, and A-3) and B (Hot 

Suite: B-1, B-2, and B-3). All operations with the potential to generate particulate matter were 

conducted in hoods or glove boxes, or were serviced by portable ductwork attached to an exhaust 

system. Procedural and administrative controls were in place to minimize exposure; these controls 

typically helped the health physics group to protect personnel. There were two SNM storage vaults 

located adjacent to the east wall of the facility and a security storage area designed to store materials 

in Zone A for short periods of time. 

Undetermined amounts of thorium were used in the Experimental Building in fuel fabrication 

experiments involving extrusion, rolling, cutting, milling, lathing, and casting of metal.

Critical Assembly Facility

This facility consisted of two buildings contained in a fenced area between the LINAC Complex and 

TRIGA / Experimental Area Building #1. The facility was used to conduct many critical and subcritical assembly experiments. These buildings, also referred to as Building 31, were collectively 

referred to as the Critical Assembly Facility. The buildings were used to support the Marine GasCooled Reactor (MGCR) and HTGR programs (General Atomics, 1961). In addition to these two 

buildings, a fuel assembly building was located in the area. Fuel assemblies were irradiated with 

accelerator-produced neutrons or with neutron triggers (e.g., PoBe or PuBe sources). The design of 

the fuel and assembly was such that if an undesired criticality were to occur, the fuel would either 

rapidly expand (Russell, 1967) or the sub-critical fuel beds would separate (Pound, 1974), inducing 

the neutron excursion to terminate. Criticality testing of fuel elements containing thorium was 

conducted at this facility. 

Science Laboratories

The Science Laboratories were composed of three two-story, arc-shaped buildings forming an annular 

ring around the central library and cafeteria buildings. The Science Laboratories contained 150 

individual laboratories and associated offices. Much of General Atomics’ work in chemistry, 

experimental physics, electronics, metallurgical research, reactor physics, and thermoelectricity was 

performed in these buildings. Thorium was used in the Science Laboratories for testing mixtures and 

components of fuel assemblies. Operations included grinding of thorium, high-temperature heating 
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under vacuum, and fabrication of thorium-uranium gel. 

Hot Cell Facility

The Hot Cell Facility (HCF), Building 23, was constructed in 1959 and used primarily to facilitate 

remote inspection of irradiated, highly-radioactive HTGR and TRIGA fuel (General Atomics, 1960). 

Approximately 12% of the building footprint was taken up by the hot cell (SNM-69). A hot cell was 

made up of 3 sections: the high-level cell (HLC), low-level cell (LLC), and the metallurgy cell (MC). 

The HLC was used as a remotely operated “hot” machine shop to cut open and section irradiated fuel 

samples for inspection. The MC was used for analytical inspection and research activities, including 

the sample preparation that entailed grinding, polishing, and mounting. The LLC was used as an 

interface between the other “hot” cells and other areas of the building, and housed all shipping cask 

off-loading and packaging operations. Thick (up to 42-inch), high-density concrete walls were in 

place to minimize personnel exposure to penetrating radiation. In addition to uranium and other fuel 

constituents, thorium materials were handled in the hot cell facility. 

Waste Yard/Incinerator

The waste processing facility includes several buildings, collectively referred to as Building 25. The 

facility was used for waste handling, minimization, processing, and storage; SNM and by-product 

material storage; and as a gamma-counting facility. Liquid wastes generated on the site were treated 

by placing them in evaporation pools. Only authorized personnel were allowed into the fenced-off 

incinerator area; they were required to wear a film badge and a self-reading dosimeter, and to submit 

bioassay samples for analysis (SNM-69). Several locations were used within the waste processing 

facility area to store radioactive materials, including TRIGA Hot Storage, a temporary storage yard, 

the Butler Building, and the By-Products Vault. Radioactive materials containing thorium were 

volume-reduced at, stored at, and shipped from the Waste Yard. Information regarding the total 

quantities and activities of individual radionuclides handled at the Waste Yard has not been identified. 

Reactor Facilities

Three separate TRIGA reactors (Mark I, Mark F, and Mark III) were operated within Building 21; 

each reactor was individually licensed (R-38, R-67, and R-100, respectively). The original building, 

constructed in 1957, housed the Mark I reactor. The building was later expanded to the east and then 

to the north (1966) to house the Mark F and III reactors, respectively. The Mark I, F, and III reactors 

were all below-ground pool reactors (General Atomics, 1966-1969). They were designed to: provide 

university training; provide a source of neutrons and/or gamma radiation for research; aid 

investigations of the effects of radiation on materials; and produce radioisotopes.

The Mark I, which was graphite-reflected, was operated routinely at steady-state thermal levels up to 

250 kW; it could also be operated in pulsed mode. The Mark F reactor (also known as the Advanced 

TRIGA Prototype and the FLAIR [Flash Irradiation Reactor]), which was water-reflected, operated 

routinely at steady-state thermal power levels up to 1500 kW and also could be operated in pulsed 

mode. The Mark III reactor, also water-reflected, operated routinely at steady-state thermal levels up 

to 1500 kW. 

The core of the TRIGA reactor contained reactor fuel, dummy fuel assemblies, and one or more 

neutron source holders. Workers may have been exposed to external and internal radiation during fuel 
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loading and maintenance. Thorium was a fuel mixture constituent during some of these operations. 

Other Locations

Due to the diversity of General Atomics operations, there was a significant potential for thorium 

storage, handling, or use in any of the buildings or work areas associated with radiological activities. 

For instance, thorium was likely handled in a radiochemistry laboratory located in the Maintenance 

Building, and the Service Building was used for receiving and shipping radioactive materials and 

components. Based on available information, NIOSH cannot rule out the possible existence of 

thorium contamination in any General Atomics radiological work area. Consequently, all General 

Atomics radiological work areas are included in the proposed SEC class.

4.2 Radiation Exposure Potential from Operations

The General Atomics source term includes depleted, normal, and highly enriched uranium (typically 

greater than 20% and up to 93.5% U-235 by mass) in the form of scrap and reactor fuel both in a fresh 

form and in an irradiated form that includes uranium as well as activation and fission products. 

Thorium was used in fuel fabrication work. Plutonium work also occurred on the site. Four linear 

accelerators (LINACs) and several nuclear reactors were also available. Sealed sources were used for 

instrument calibrations and other work. Byproduct materials (atomic numbers 3 to 83) and tritium 

were also used.

The potential for external radiation dose existed at all the General Atomics facilities that conducted 

radiological work. The areas known to NIOSH as radiological work areas include: Science 

Laboratories A, B, and C (Building 2); Experimental Building (Building 9); Maintenance (Building 

10); Service Building (Building 11); Buildings 21 and 22; Hot Cell Facility (Building 23); Waste Yard 

(Buildings 25 and 26); Experimental Area (Buildings 27 and 27-1); LINAC Complex (Building 30); 

HTGR-TCF (Building 31); Fusion Building (Building 33); Fusion Doublet III (Building 34); SV-A 

(Building 37); SV-B (Building 39); and SV-D (no building number). Based on the site operations 

outlined in Section 4.1, sources of exposure included photons and neutrons emitted from the reactors 

and the LINACs and neutron from sources such as Pu-Be and Am-Be.

The primary sources of internal radiation exposure at the site were uranium isotopes (depleted, 

natural, enriched, and recycled), plutonium, thorium, tritium, and other fission and activation products 

generated during various processes at General Atomics.

Determining the amount and variety of radionuclides comprising the source term for radiological

exposures at General Atomics is a difficult process due to changes in radionuclides over time as well 

as fluctuations in SNM inventory on the site. The number of laboratories, and the variety of 

laboratory activities associated with work in chemistry, experimental physics, electronics, 

metallurgical research, reactor physics, and thermoelectricity, led to the potential for a large variety of 

radionuclides as well as varying quantities of these radionuclides on the site at any given time 

(ORAUT-TKBS-0045, PDF p. 40). 

Building 23, HCF (which contained BeO, EBOR, tritium production, and a room where plutonium 

was handled) was also referred to as the Plutonium Laboratory. In late 1959, during the final phase of 

construction, General Atomics decided to expand the original building design to include an additional 

1,200 ft2 of laboratory space to accommodate the EBOR Fuel Fabrication Facility. Portions of the 
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building have been used to conduct other radiological activities, including the development and 

manufacture of EBOR fuel (in Rooms 108/108A), a tritium extraction laboratory for preparation and 

testing of irradiated fuel samples in Room 109 from 1969 to 1987, and a plutonium transport 

experiment that used plutonium oxide (Room 116). General Atomics conducted the SNAP-15A 

Program for AEC, which utilized a small thermoelectric generator that was powered by Pu-238. 

General Atomics also documented the presence of plutonium on the site in October 1964 when the 

SNAP-15A Plutonium Handling Room was completed at the SV-B Building (Bold, 1964), but 

plutonium was probably handled elsewhere on the site earlier. The SNAP Plutonium Handling Room 

was later relocated to the Experimental Building concrete vault in October 1965 (ORAUT-TKBS0045, PDF pp. 37-38).

Thorium in the form of oxides, carbides, and nitrates was documented at General Atomics. Thorium 

was used for fabrication of thorium-uranium fuel. Thorium appears to have been on the site before 

and throughout the AWE operational period. Some of the operations at the HCF and Experimental 

Critical Facility involved irradiated, experimental HTGR fuels for a thorium fuel cycle and irradiated 

fuel for the Reduced-Enrichment Research and Test Reactor (RERTR) program. The HTGR design 

employed two types of fuel, both in the physical form of microspheres. No in vitro bioassay results 

specifically for thorium have been found for General Atomics. There does not appear to be a 

defensible way to ratio thorium intakes to uranium intakes because some tasks included pure thorium 

handling. Thorium source terms that were associated with internal exposures would have most 

commonly been associated with the Fuel Fabrication Facility, the Scrap Handling Facility, the 

laboratory buildings, the Experimental Building High Bay and HTGR critical assembly, and the waste 

handling areas. 

General Atomics conducted research and development on thermoelectric generators that were

powered by radioisotopes for space power applications for AEC. By the end of September 1964, a

250-W 90Sr-powered thermoelectric generator had been investigated and test generators were being 

fabricated and tested (General Atomics, 1964). Radioactive strontium was associated with the 

irradiated fuels and the Y-90 Production Facility. Specific information on chemical form or forms of 

Sr-90 at General Atomics has not been found by NIOSH, but strontium that is associated with the 

irradiated fuels is likely to be in the form of an oxide and strontium used for the production of nuclear 

batteries (thermoelectric generators) may have been in the form of SrTiO3 (ORAUT-TKBS-0045). 

Other fission products were associated with irradiated fuel and reactor operations. General Atomics 

documentation mentions Cs-134, Cs-137, and Ta-182 and Eu-154 (ORAUT-TKBS-0045). Monthly 

reports in the mid-1960s discuss the use of titanium tritide associated with the TRIGA Reactor 

Building. It appears that targets were irradiated in the TRIGA reactor and then the Activation 

Analysis group worked with the targets in the Experimental Area Building #1 – Bunker (ORAUTTKBS-0045, PDF p. 20).

The TRIGA reactors and the LINAC were used to activate a variety of materials including soils, steel, 

cladding materials, uranium, and plutonium. A detailed list of possible activation products at the 

LINAC is provided in Attachment F of ORAUT-TKBS-0045.

Little information has been found on the quantities and chemical forms of tritium that were

used at General Atomics during the AWE period, but site documentation indicates that a Texas 

Nuclear Corporation Neutron Generator console at the LINAC was being used with a “new 3 to 5 
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curie tritium target” in January 1963 (Bold, 1963). The October 1965 monthly report for TRIGA and 

Activation Analysis Facilities (Cockle, 1965) noted that 25 used tritium targets that totaled

111 Ci were transferred from General Atomics for storage and ultimate disposal. Tritides (particulate) 

and tritiated water vapor and tritiated gas (the latter compounds would be released during off-gassing 

of the tritium targets) were likely chemical forms on the site.

4.3 Time Period Associated with Radiological Operations

Per the DOE Office of Health, Safety and Security (HSS), the time period associated with AWE 

operations at General Atomics is from January 1, 1960 through December 31, 1969, as specified by 

DOE HSS (https://hsspublic.energy.gov/search/facility/ViewByName.aspx). NIOSH has discovered 

no additional data to support more specific dates for the start and stop of AWE operations. Therefore, 

AWE work at General Atomics is assumed to have started on January 1, 1960, and to have continued 

through December 31, 1969.

4.4 Site Locations Associated with Radiological Operations

The General Atomics facility was comprised of many buildings where many different activities 

occurred. These activities required the use of test reactors, fusion reactors, LINACs, hot cells, and 

radiochemistry laboratories; many of these operations involved uranium, plutonium, and thorium. 

• Building 2 held radiological and chemical laboratories. 

• Building 9 was the site of radiological operations, including fuel element development and Pu 

storage. 

• Building 10 had a radio-analytical laboratory. 

• Building 11 was used for shipping and receiving radioactive materials. 

• Building 21 housed three TRIGA reactors. 

• Building 22 was for TRIGA Fuel Fabrication. 

• Building 23 housed the Hot Cell Facility.

• Buildings 25 and 26 were for waste storage, SNM storage, and housed a gamma counting facility.

• Building 27 was for preparing target samples for neutron irradiation and post-irradiation 

radiochemical separations.

• Building 27-1, also known as the “Experimental Area Building #1 – Bunker” contained the

Strontium Facility and was the location for neutron activation, yttrium production, and research 

and development.

• Building 30 was the LINAC Complex that housed the high-energy electron accelerators.

• Building 31 was the Critical Assembly Facility used for testing fuel elements.

• Building 33 was the Fusion Building for studying controlled thermonuclear reactions.

• Building 34 housed the Fusion Doublet III for research in magnetic fusion technologies.

• Building 37 was for fabricating fuel elements.

• Building 39 was for fabrication and testing fuel assemblies for HTGR.

• Building SV-D stored assembled thermionic and thermoelectric fuel elements. 

Records suggest that thorium was routinely used in nine of the buildings specified above. However, 

based on available documentation (General Atomics, 1964; SNM-696) the transfer, storage, and use of 

thorium in other radiological buildings was also likely. Through the course of ongoing dose 
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reconstruction and research associated with the SEC-00064 class period, NIOSH has determined that, 

due to undocumented worker movements across the site, limited claimant-specific information 

pertaining to work locations, and observation that employment records do not always indicate work 

locations, NIOSH is unable to eliminate any specific worker from potential exposure scenarios based 

on assigned work location. NIOSH is therefore unable to define individual worker exposure scenarios 

based on specific work locations within the General Atomics site during the period under evaluation.

4.5 Job Descriptions Affected by Radiological Operations

NIOSH has determined that the site-specific and claimant-specific data available for General Atomics

for the time period under evaluation are insufficient to allow NIOSH to determine that any specific 

work group was not potentially exposed to external radiation fields, radioactive material releases, or 

possible subsequent contamination.

NIOSH has insufficient information associating job titles and/or job assignments with specific

radiological operations or conditions. Without such information, NIOSH is unable to define potential 

radiation exposure conditions based on worker job descriptions.

5.0 Summary of Available Monitoring Data for the Proposed Class

The primary data used for determining internal exposures are derived from personal monitoring data, 

such as urinalyses, fecal samples, and whole-body counting results. If these are unavailable, the air 

monitoring data from breathing zone and general area monitoring are used to estimate the potential 

internal exposure. If personal monitoring and breathing zone area monitoring are unavailable, internal 

exposures can sometimes be estimated using more general area monitoring, process information, and 

information characterizing and quantifying the source term.

This same hierarchy is used for determining the external exposures to the cancer site. Personal 

monitoring data from film badges or thermoluminescent dosimeters (TLDs) are the primary data used 

to determine such external exposures. If there are no personal monitoring data, exposure rate surveys, 

process knowledge, and source term modeling can sometimes be used to reconstruct the potential 

exposure.

A more detailed discussion of the information required for dose reconstruction can be found in 

OCAS-IG-001, External Dose Reconstruction Implementation Guideline, and OCAS-IG-002, Internal 

Dose Reconstruction Implementation Guideline. These documents are available at: 

http://www.cdc.gov/niosh/ocas/ocasdose.html.

5.1 Data Capture Efforts and Sources Reviewed 

As a standard practice, NIOSH completed an extensive database and Internet search for information 

regarding General Atomics. The database search included the DOE Legacy Management Considered 

Sites database, the DOE Office of Scientific and Technical Information (OSTI) database, the Energy 

Citations database, and the Hanford Declassified Document Retrieval System. In addition to general 

Internet searches, the NIOSH Internet search included OSTI OpenNet Advanced searches, OSTI 

Information Bridge Fielded searches, Nuclear Regulatory Commission (NRC) Agency-wide 

Documents Access and Management (ADAMS) web searches, the DOE Office of Human Radiation 
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Experiments website, and the DOE-National Nuclear Security Administration-Nevada Site Officesearch. Attachment One contains a summary of General Atomics documents. The summary 

specifically identifies data capture details and general descriptions of the documents retrieved.

In addition to the database and Internet searches listed above, NIOSH identified and reviewed 

numerous data sources to determine information relevant to determining the feasibility of dose 

reconstruction for the class of employees under evaluation. This included determining the availability 

of information on personal monitoring, area monitoring, industrial processes, and radiation source 

materials. The following subsections summarize the data sources identified and reviewed by NIOSH.

5.2 Previous Dose Reconstructions

NIOSH reviewed its NIOSH DCAS Claims Tracking System (referred to as NOCTS) to locate 

EEOICPA-related dose reconstructions that might provide information relevant to the petition 

evaluation. NIOSH also reviewed each claim to determine whether internal and/or external personal 

monitoring records could be obtained for the employee. Table 5-1 summarizes the results of this 

review. (NOCTS data available as of June 11, 2014)

Table 5-1: No. of Site Name Claims Submitted Under the Dose Reconstruction Rule

Description Totals

Total number of claims submitted for dose reconstruction 145

Total number of claims submitted for energy employees who worked during the period under 

evaluation (January 1, 1960 through December 31, 1969) 107

Number of dose reconstructions completed for energy employees who worked during the period 

from January 1, 1960, through December 31, 1969 (i.e., the number of such claims completed by 

NIOSH and submitted to the Department of Labor for final approval).

59

Number of claims for which internal dosimetry records were obtained for the period from January 1, 

1960, through December 31, 1969 78

Number of claims for which external dosimetry records were obtained for the identified for the 

period from January 1, 1960, through December 31, 1969 58

5.3 Worker Interviews

The specific purpose of this evaluation is to expand the existing class description associated with 

SEC-00064 by removing the area-specific and monitoring criteria from the class parameters. As such, 

NIOSH has determined that additional interviews supporting this evaluation were not necessary, and 

therefore were not performed.

5.4 Internal Personnel Monitoring Data

During the AWE operational period for General Atomics (1960 through 1969), some workers were 

monitored by bioassay; however, bioassays were not routine at General Atomics until October 1963. 

NIOSH has reviewed available data, which appear to be from random sampling, and identified 1,188 

bioassay results through September 1963. NIOSH has identified 1,577 bioassay records for the period 

October through December 1963. These results are gross activity results. NIOSH has identified 

17,188 results from October 1963 through December 1969. According to the data available to 
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NIOSH, most results were for in vitro sampling. A majority of the samples collected from 1960 

through 1963 were analyzed for gross beta, gross alpha, and U-235. Most of the in vitro bioassay data 

available for the period October 1963 through December 1969 show that samples were analyzed for 

gross alpha or for uranium activity. The bioassay program incorporated gross counting methods to 

determine exposure to uranium, and the analytical methods used are generally unavailable to NIOSH. 

Determination of the specific internal exposures to other radionuclides, including thorium-232, 

thorium-238, plutonium, and americium, did not occur within the AWE operational period (ending 

December 31, 1969). NIOSH has located no in vitro results specifically for exposure to thorium. 

Further, NIOSH has not found any evidence to suggest that routine or job-specific in vitro bioassay 

for thorium exposure was performed at General Atomics. 

Strontium analyses involved chemically removing the strontium from the urine sample, counting the 

new sample, and counting again when the Y-90 has started to grow back in order to determine the 

activity of Sr-90. Strontium could have been associated with irradiated fuels or the Y-90 Production 

Facility (about which little is known), as well as other programs (ORAUT-TKBS-0045, PDF pp. 56-

57).

General Atomics began monitoring for tritium exposure by bioassay in September 1965. NIOSH has 

identified 194 tritium bioassay records for the period November 1965 through December 1969. 

NIOSH’s 2006 evaluation for SEC-00064 determined that it is not feasible to reconstruct internal 

radiation doses from exposure to tritium before October 1965 (ORAUT-TKBS-0045, PDF p. 58). The 

type of metal tritides potentially present at General Atomics is important for accurate assessment of 

internal dose since metal tritides exhibit different characteristics depending on their formulation. For 

example, compared to HTO which is classified as Type F, titanium tritide studies have reported it to 

be Type M or S materials in terms of dissolution classification. If the metal tritide is zirconium tritide, 

then it would be classified as Type S. If all tritium is in the form of insoluble Type S metal tritide, a 

urinalysis program could fail to detect rather large intakes. There is no information on whether any 

analyses were performed on the type of metal tritides that may have been present at General Atomics, 

and what the potential for intake might have been during the AWE period.

Urine samples that contained mixed fission and activation products were likely placed in a container 

and gamma-counted, or evaporated to dryness and beta-counted. The radionuclides were typically not 

identified, and the results were reported in terms of gross activity or gross beta and adjusted to a 24-

hour time if a 24-hour sample was not provided or analyzed (ORAUT-TKBS-0045, PDF p. 58).

At some point, maybe in 1963, the urine samples were chemically processed and then beta-counted, 

but it is not known if the gamma-counted results were chemically processed or if results that were 

designated as MFPs or beta represent the same or different analysis types (ORAUT-TKBS-0045, PDF 

p. 58).

No explicit concentration measurements of thoron progeny have been found for 1960 through 1969. 

Given the fairly routine references to contamination on air samples from thoron progeny in the Fuel 

Fabrication area during the 1960-1969 period, and the lack of information about what activities took 

place at the Thorium Pilot Plant after AWE operations, NIOSH assumes that the later Pilot Plant 

measurements are not useful for estimating thoron concentrations during the operational period in 

areas where large quantities of thorium were stored and handled.
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General Atomics implemented an in vivo analysis program in 1966. The Helgeson mobile counter 

was brought to the site a few times each year. The perceived potential for internal exposure was the 

early basis for including a worker in the in vivo bioassay program. Many individual measurement 

spectra are included with results identifying the radionuclide and quantity measured. Background and 

calibration measurements were also observed in the records provided by Helgeson (Helgeson, 1966). 

The first U-235 lung counting results (~1966 through 1967) were considered "experimental" by 

Helgeson, and were either associated with some large uncertainty or assumed to be invalid. Workers 

were chosen for lung counts based on their potential for U-235 exposure and the results of their 

uranium urinalyses (Helgeson, 1969). The early General Atomics U-235 in vivo measurements are 

indicators that a worker had the potential for U-235 exposure. 

In addition to the Helgeson in vivo analysis, General Atomics conducted its own in-house in vivo 

measurements beginning in 1966. The subject sat in an office chair lined with 0.25-inch thick lead 

and a 4” x 4” NaI(Tl) detector operated in a lap geometry. 

The in vivo bioassay program was not used in 1966 to routinely monitor for exposures to thorium, 

although twelve workers were analyzed for thorium in March of that year. These results were 

reported to be experimental and final results were not provided by Helgeson (Helgeson, 1966). 

Available records indicate that a thorium in vivo result was reported for only one worker in 1969, who 

was reported to have no thorium activity (Helgeson, 1969). 

5.5 External Personnel Monitoring Data

External whole body dosimetry results are available for monitored General Atomics workers for the 

entire AWE operational period (January 1960 through December 1969). NIOSH has 27,661 external 

monitoring records available for that period. Initially, external dosimetry services using film badges 

were provided by R. S. Landauer, Jr. and Company. In July 1961, those services were transferred to 

Radiation Detection Company; however, in 1965 they were transferred back to R. S. Landauer, Jr. and 

Company. Personnel working in areas where potential neutron exposure could occur were issued film 

badges sensitive to beta, gamma, and neutron radiation. Otherwise, personnel were issued film badges 

sensitive to only beta and gamma radiation. 

No details on the Radiation Detection Company dosimeter design or film type are currently available,

but site documentation suggests that the film badge was comparable to the Landauer design. Film 

badge detection thresholds for R.S. Landauer, Jr. and Company badges were reported in January 1961 

as 10 mrem from gamma, 40 mrem from beta, and 20 mrem from fast neutrons. Other documentation 

indicates that film badge detection thresholds in the early days were assumed to be as high as 50 mrem 

for gamma and 60-80 mrem for beta. 

In addition to the badge dosimeters, personnel used direct- or indirect-reading dosimeters, such as 

personal ion chambers. It is unclear whether these additional dosimeters detected low-energy X-rays. 

(Currently available pocket dosimeters designed for low-energy X-ray detection report the lower end 

of the energy range as 20 to 40 keV. Dosimeters not specifically designed for low-energy X-ray 

detection have thresholds of about 80 keV.) Extremity dosimeters were used in some operations, such 

as during removal of irradiated samples from the TRIGA reactors (Gurren, 1966). Results from the 

pocket dosimeters were logged by staff on a routine basis. Some on-site readings are included in the 
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available individual dosimetry records. 

Site documentation indicates that during the 1960 to 1961 timeframe, film badges, fast and thermal 

neutron detection equipment, and direct- and indirect-reading pocket dosimeters were irradiated to 

evaluate the radiation recorded on each device. Beginning in early 1960, indium foils were 

incorporated into personnel security badges in case of a criticality event (Ray, 1960). By July 1961, 

all personnel film holders were equipped with a built-in threshold detector for neutron dose 

evaluations in the event of a criticality (Bold, 1961). Badges were exchanged on a bi-monthly 

frequency at General Atomics in 1960 and 1961 (Bold, 1962). In 1962, badges were exchanged 

monthly (Bold, 1968); this frequency was likely used until 1996 when quarterly exchanges were 

begun.

According to 1961 correspondence, “Special Tests for Employees Working Around BeO,” special 

radiation tests, X-rays, and spirograms were conducted for employees working in the vicinity of BeO 

(Bethard, May1961, Bethard, Jun1961, Bethard, Sep1961, and 1961d). No additional documentation 

detailing occupationally-required medical X-ray examinations has been identified. NIOSH’s review 

of data for EEOICPA claimants who worked at General Atomics suggests that X-rays were given 

annually. To date, no information regarding equipment and techniques specific to General Atomics 

has been located. 

5.6 Workplace Monitoring Data

Engineering controls to reduce radiation/radioactivity exposure appear to have been present 

throughout the site. General Atomics conducted routine air monitoring, but noted inadequacies in the 

frequency and quality of its program in the early years. NIOSH has no documentation that suggests 

thorium was specifically monitored by air sampling. 

Surface area wipe-testing was performed periodically at General Atomics, but it is unclear whether 

direct contamination surveys were routinely performed. Several incidents involving radioactivity 

releases and occurrences of contamination were documented (Hughes, 1964; Hughes, 1967; Hughes, 

1969; Kesting, 1964; Kesting, 1969; Lepper, 1963). At least one incident, in 1968, involved the 

LINACs whereby both long- and short-lived radionuclides were potentially released. Because 

thorium was irradiated at the accelerators, it is plausible that thorium was released during one or more 

incidents.

5.7 Radiological Source Term Data

Much of the information specifying the radioactive isotopes and their quantities used, produced, 

and/or fabricated at General Atomics from January 1, 1960 through December 31, 1969 are not 

available to NIOSH. However, it is clear that various radionuclides, such as TRIGA fuel, were 

present at General Atomics during that period. It is possible to obtain a snapshot of allowable 

quantities of radioactive material at General Atomics from radioactive material licenses. Table 5-2 

presents summary information available to NIOSH regarding licensed quantities during the period

from 1960 through 1969 (ORAUT-TKBS-0045; SNM-69, PDF pp. 9-11). Radionuclides and 

allowable quantities might have changed over time, but based on site descriptions, health physics 

reports, and inventory reports, the materials listed in Table 5-2 are generally representative of the 

variety and the upper limits on source term during the AWE covered period. 
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Table 5-2: Allowable Quantities of Radioactive Material at General Atomics

Date License Material Description Form Quantity Total

ca. 1960

AEC License 

No. 4-1611-11 

(J-60) 

Byproduct materials, 

atomic numbers from 

3 through 83 

Any 10 Ci each 500 Ci 

H-3 200 mCi 

Sr-90 Sealed 1 Ci 

Sr-90 Unsealed 100 mCi

Po-210 Sealed 50 Ci 

Po-210 Unsealed 100 mCi 

Tm-170/171 50,000 Ci 

Dec. 1960 

AEC License 

No. 4-1611-11 

(J-60), proposed 

increase 

Byproduct materials, 

atomic numbers 3 

through 83 

Any 100,000 Ci 

each 500,000 Ci 

Proposed 

addition Fission products All 1,000,000 Ci 

May 1965 SNM-69 Uranium As metal or 

metallic alloy

300 kg 

(up to 20% 

enriched U235)

U-235

As metal, 

metallic 

alloy, or 

compounds

265 kg 

(up to 93.5% 

enriched in 

U-235)

U-233

As metal, 

metallic 

alloy, or 

compounds

100 gm 

(any 

enrichment)

U-235 In sealed 

containment

50 gm 

(up to 93.5% 

enriched in 

U-235)

U-233 In sealed 

containment

32 gm 

(any 

enrichment)

Plutonium In sealed 

containment

1095 gm 

(any 

enrichment)

Plutonium

Unseparated, 

bred 

fissionable 

material

1 gm
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6.0 Feasibility of Dose Reconstruction for the Proposed Class

42 C.F.R. § 83.14(b) states that HHS will consider a NIOSH determination that there was insufficient 

information to complete a dose reconstruction, as indicated in this present case, to be sufficient,

without further consideration, to conclude that it is not feasible to estimate the levels of radiation 

doses of individual members of the class with sufficient accuracy. 

In the case of a petition submitted to NIOSH under 42 C.F.R. § 83.9(b), NIOSH has already 

determined that a dose reconstruction cannot be completed for an employee at the DOE or AWE 

facility. This determination by NIOSH provides the basis for the petition by the affected claimant. 

Per § 83.14(a), the NIOSH-proposed class defines those employees who, based on completed 

research, are similarly affected and for whom, as a class, dose reconstruction is similarly not feasible.

In accordance with § 83.14(a), NIOSH may establish a second class of co-workers at the facility for 

whom NIOSH believes that dose reconstruction is similarly infeasible, but for whom additional 

research and analysis is required. If so identified, NIOSH would address this second class in a 

separate SEC evaluation rather than delay consideration of the claim currently under evaluation (see 

Section 10). This would allow NIOSH, the Board, and HHS to complete, without delay, their 

consideration of the class that includes a claimant for whom NIOSH has already determined a dose 

reconstruction cannot be completed, and whose only possible remedy under EEOICPA is the addition 

of a class of employees to the SEC.

This section of the report summarizes research findings by which NIOSH determined that it lacked 

sufficient information to complete the relevant dose reconstruction and on which basis it has defined 

the class of employees for which dose reconstruction is not feasible. NIOSH’s determination relies on 

the same statutory and regulatory criteria that govern consideration of all SEC petitions.

6.1 Feasibility of Estimating Internal Exposures

NIOSH has evaluated the available personnel and workplace monitoring data and source term 

information, and has determined that there are insufficient data for estimating internal exposures, as 

described below.

As stated in Section 3.0 of this report, HHS has designated an SEC class for General Atomics workers 

for the period from January 1, 1960 through December 31, 1969 (HHS, 2007). In the class 

designation letter,

HHS states:

(1) General Atomics AWE employees in the proposed class could have received internal and external 

radiation exposures from uranium, thorium, plutonium, and other radioactive materials.

(2) NIOSH lacks sufficient information, including biological monitoring data, air monitoring 

information and process and radiological source information, that would allow it to estimate the 

potential intakes(s) of thorium, and the resulting dose to which the proposed class may have been 

exposed for the period from January 1, 1960, through December 31, 1969.

(3) Pursuant to 42 C.F.R. § 83.13(c)(I), NIOSH determined that there is insufficient information 

either to estimate the maximum radiation dose for every type of cancer for which radiation doses 
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are reconstructed that could have been incurred under plausible circumstances by any member of 

the class, or to estimate the radiation doses of members of the class more precisely than a 

maximum dose estimate.

(4) Although NIOSH is unable to adequately estimate total internal exposures for members of the 

class, internal dose due to intake of uranium can be reconstructed for exposures starting in 

October 1963, and tritium internal dose can be estimated after September 1965. NIOSH considers 

the reconstruction of occupational external radiation doses, including medical dose to be feasible 

for members of the class

.

The associated SEC class designated by HHS included only those employees who worked in Science 

Laboratories A, B, and C (Building 2); Experimental Building (Building 9); Maintenance (Building 

10); Service Building (Building 11); Buildings 21 and 22; Hot Cell Facility (Building 23); Waste Yard 

(Buildings 25 and 26); Experimental Area (Buildings 27 and 27-1); LINAC Complex (Building 30); 

HTGR-TCF (Building 31); Fusion Building (Building 33); Fusion Doublet III (Building 34); SV-A 

(Building 37); SV-B (Building 39); and SV-D (no building number).

The 2007 class description was based on the NIOSH determination that exposure potential was 

limited to workers in these buildings, that all workers with the potential for radiation exposures during 

the proposed SEC class time period were included in the external dose monitoring program, and that 

unmonitored workers had no potential for radiation exposures.

A NIOSH review of existing SEC class definitions evaluated criteria such as consistency, 

applicability, and whether any class definitions needed to be corrected by NIOSH (DCAS, 2010). In 

this review NIOSH determined that the class definition recommended in its 2006 evaluation of SEC00064 needed revising because of the potential for difficulties in implementing the class definition. In 

addition, through the course of ongoing dose reconstruction and research, NIOSH has determined that, 

due to undocumented worker movements across the site, limited claimant-specific information 

pertaining to work locations, and observation that employment records do not always indicate work 

locations, NIOSH is unable to eliminate any specific worker from potential exposure scenarios based 

on assigned work location. NIOSH has found that a determination cannot always be made as to the 

specific area an employee worked in, or whether an employee should have been monitored for 

radiological exposures. 

Accordingly, NIOSH has determined that it is necessary to remove the area-specific and monitoring 

criteria from the class description associated with SEC-00064 thorium exposures for the period from 

January 1, 1960 through December 31, 1969. As such, NIOSH recommends expanding the SEC class 

definition to include all areas of the General Atomics facility, and to include all employees of Atomic 

Weapons Employees who worked for General Atomics during the period from January 1, 1960 

through December 31, 1969.

Also through the course of ongoing dose reconstruction and methodology reviews conducted by 

NIOSH and the Board after implementation of SEC-00064, the following issues have been identified 

that may pertain to assessing internal exposures during the General Atomics period from 1960 through 

1969:

• Using non-contemporaneous data to estimate exposures during the AWE operational period
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o Concerns were raised regarding the use of long-lived gross airborne alpha activity observed in 

the Fuel Fabrication Facility from 1965 through 1968 to estimate exposures during earlier time 

periods (i.e., 1960 through 1964). Concerns were also raised regarding the use of 

radionuclides observed in the high-level cell area in 1994 to estimate plutonium exposures 

throughout the facility during the earlier AWE operational period. 

o Applying air sample results from one period to other periods and locations relies on the 

assumption that the relative quantities of radionuclides used and the work practices 

remained the same throughout various time periods and locations.

o NIOSH has little information regarding inventory of the materials used in the Fuel 

Fabrication Facility and whether the type of work conducted changed during the AWE 

period. The licenses include various quantities of isotopes of uranium, plutonium, natural 

thorium, fission products, and activation products. It is known that General Atomics 

employees worked with these radionuclides throughout the AWE period. The fuel 

fabrication work moved from the Experimental Building to the Fuel Fabrication Facility in 

1962 (ORAUT-TKBS-0045, PDF p. 25).

o Available site documentation indicates that supplied air hoods were required in the thorium 

process area of the Fuel Fabrication Facility by January 1966 (ORAUT-TKBS-0045, PDF 

p. 44), possibly indicating that work or work process at the facility may have changed 

around that period.

o Because NIOSH does not have access to records indicating time periods, locations, and the 

quantities of uranium, plutonium, and thorium present, their isotopic ratios as well as their 

relative isotopic ratios of airborne activity cannot be established with any degree of 

confidence. Thus, there does not appear to be a defensible way to extrapolate airborne 

exposure for the 1960-1964 period from the long-lived gross airborne alpha activity 

observed during the 1965-1968 period. 

• Gross alpha procedures used during the AWE period

o Concerns were raised regarding the gross alpha procedures that were used during the AWE 

operational period. There are indications that little consideration was given to the presence of 

plutonium isotopes, as well as americium and other alpha emitters in the samples. 

o The explanation for bioassay codes in ORAUT-TKBS-0045, Table 3-1 states that uranium 

urinalysis (results written as U-235 in urine) can be assumed to be total uranium. These 

samples could either have been analyzed by fluorimetry or gross-alpha counting. Any alpha 

emitter that made it through the chemical processing of the urine would be detected by the 

gross-alpha counting methods, but the actual chemical recovery for non-uranium alpha 

emitters is unknown, so only uranium is assumed (ORAUT-TKBS-0045, PDF p. 49).

o If the chemical recovery of non-uranium alpha emitter is unknown, then internal dose resulting 

from intake of other radionuclides cannot be correctly accounted for. Thus, accuracy of dose 

reconstruction using such partial data is doubtful.
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• Strontium exposure/dose reconstruction

o The need was identified for a method to reconstruct internal doses to workers who might have 

been exposed to strontium during the AWE operational period, but were not part of a bioassay 

program.

o The earliest indication of presence of strontium at General Atomics is in AEC license No. 

4-1611-11 from 1960, which includes Sr-90 in sealed and unsealed forms (ORAUTTKBS-0045, PDF p. 124). The initial focus of the bioassay program appeared to be 

uranium. Bioassay before October 1963 occurred only in response to nose wipes and 

incidents and was not routine. Records of urinalysis for fission and activation products are 

available as early as 1963 (ORAUT-TKBS-0045, PDF p. 48).

o Strontium could have been associated with irradiated fuels or the Y-90 production, as well 

as other programs. 

o ORAUT-TKBS-0045 states that specific information on the chemical form(s) of Sr-90 at 

General Atomics is unavailable; although strontium that was associated with the irradiated 

fuels is likely to be in the form of an oxide and not titanate. If strontium was being used 

for the production of thermoelectric generators it might have been in the form of SrTiO3. 

o ORAUT-TKBS-0045 further suggests that in the absence of any information about the 

urine sample processing at General Atomics during the AWE period, it is favorable to the 

claimant to assume that the analysis is strontium; this results in the largest strontium values 

on which other radionuclides are based. 

o However, all of the current dose reconstruction methodologies for General Atomics 

assume that urinalysis was performed. In absence of any urinalysis because the workers 

were not part of any bioassay program, reasonable and accurate strontium dose 

reconstruction cannot be performed.

• Metal tritide exposure/dose reconstruction

o A concern was raised regarding the possible need for expanded consideration of the potential 

for exposure to metal tritides and the methods used to identify workers that might have been 

exposed to metal tritides.

o Monthly reports in the mid-1960s discuss the use of titanium tritide associated with the 

TRIGA reactor building. It appears that targets were irradiated in the TRIGA reactor and 

then the Activation Analysis group worked with the targets in the Experimental Area 

Building #1.

o Little information has been found regarding the quantities and chemical forms of tritium 

that were used at General Atomics, but site documentation indicates that a Texas Nuclear 

Corporation Neutron Generator console at the LINAC was being used with a “new 3 to 5 

curie tritium target” in January 1963 (ORAUT-TKBS-0045, PDF p. 39).
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o The October 1965 monthly report for TRIGA and Activation Analysis Facilities noted that 

25 used tritium targets that totaled 111 Ci were transferred from General Atomics for 

storage and ultimate disposal. Tritides (particulate) and tritiated water vapor and tritiated 

gas (the latter compounds would be released during off-gassing of the tritium targets) were 

likely chemical forms on the site (ORAUT-TKBS-0045, PDF p. 39).

o Various materials were used as LINAC targets, including fissile material. Documents 

mention the use of LINAC tritium targets. However, there is no information on the 

material used in the construction of the targets, the number of tritium targets, nor the 

tritium activity within the targets used in the LINAC.

o If all tritium is in the form of insoluble (Type “S”) metal tritide, a urinalysis program could 

fail to detect rather large intakes, which could result in correspondingly large missed doses, 

particularly to the lung.

o There is no information on whether any analyses were performed on the type(s) of metal 

tritide that may have been present at General Atomics, nor on what the potential intake by 

workers might have been during the AWE period. Thus, without the knowledge of the 

type of metal tritide and the fraction of tritium intake that the metal tritide may represent, 

sufficiently accurate internal dose assessment cannot be made.

• Plutonium-241 exposure/dose reconstruction

o A concern was raised regarding the possible need for an expanded consideration of plutonium241 exposures. Pu-241 has a 14-year half-life and decays to Am-241 through beta emission.

o Table E-1 in Attachment E of ORAUT-TKBS-0045, provides information on the types of 

work and radiological monitoring that were performed at the Plutonium Laboratory in the 

HCF. The work appears to have involved mostly unencapsulated fuel-grade plutonium in 

glove boxes (ORAUT-TKBS-0045, PDF p. 38).

o ORAUT-TKBS-0045 states that at the HCF Plutonium Laboratory the beta-activity 

fraction was as high as or higher than the alpha-activity fraction, possibly due to the 

presence of Pu-241, which might have been significant (about 85%) in terms of activity in 

a Pu-239/Pu-240 source term. With the maximum energy beta emissions of 21 keV, Pu241 would be difficult to detect unless a windowless counter was used. But it is possible 

that the photon emissions from the plutonium isotopes and Am-241, as well as the 

bremsstrahlung from the Pu-241 beta emissions, were detected and attributed to beta 

emissions (ORAUT-TKBS-0045, PDF p. 38).

o Documentation available to NIOSH does not mention Am-241 in association with the 

plutonium source term. For fresh source terms the Am-241 activity would be insignificant, 

but after 5 years the Am-241 in-growth would account for approximately 8% of the total 

radioactivity in an unirradiated reactor fuel-grade source term. 

o Thus, it is possible that Pu-241 could have escaped detection or its presence could have 

been attributed to other isotopes. Moreover, without the knowledge of whether Pu-241 
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went undetected or was erroneously identified as other isotopes, and the lack of 

information on the magnitude of the missed activity, sufficiently accurate Pu-241 dose 

construction cannot be performed.

• Thoron exposure/dose reconstruction

o Concerns were raised regarding the use of thoron measurements performed at the Pilot Plant 

during post-operations to characterize possible thoron exposures during AWE operations.

o No explicit concentration measurements of thoron or its progeny have been found for 1960 

through 1969. A later set of measurements from 1975 is not considered representative of

the 1960-1969 period (ORAUT-TKBS-0045, PDF p. 47).

o ORAUT-TKBS-0045 states that given the fairly routine references to contamination on air 

samples from thoron progeny in the fuel fabrication area and the lack of information about 

what activities took place at the Thorium Pilot Plant, it seems unreasonable to assume that 

these later Pilot Plant measurements are useful for estimating thoron concentrations during 

the operational period in areas where large quantities of thorium were stored and handled 

(ORAUT-TKBS-0045, PDF p. 61). 

Due to the issues indicated above, NIOSH has determined that infeasibilities associated with 

sufficiently accurate reconstruction of internal exposures during the period from January 1, 1960 

through December 31, 1969 extend beyond the assessment of thorium exposures, as was presented in 

NIOSH’s 2006 evaluation of SEC-00064. NIOSH does not have access to sufficient personnel 

monitoring, workplace monitoring, or source term data to estimate potential internal exposures to 

unmonitored radionuclides, including unmonitored uranium, thorium, plutonium, tritium, and fission 

and activation products, during the period of AWE operations. Consequently, NIOSH finds that it is 

not feasible to estimate, with sufficient accuracy, internal exposures to unmonitored radionuclides, 

including unmonitored uranium, thorium and progeny, plutonium, tritium, and fission and activation 

products, and resulting doses for the class of employees covered by this evaluation.

Although NIOSH found that it is not possible to completely reconstruct internal radiation doses for the 

proposed class, NIOSH intends to use any internal monitoring data that may become available for an 

individual claim (and that can be interpreted using existing NIOSH dose reconstruction processes or 

procedures). Therefore, dose reconstructions for individuals employed at General Atomics during the 

period from January 1, 1960 through December 31, 1969, but who do not qualify for inclusion in the 

SEC, may be performed using these data as appropriate.

6.2 Feasibility of Estimating External Exposures

This evaluation responds to a petition based on NIOSH determining that internal radiation exposures 

to unmonitored radionuclides could not be reconstructed for a dose reconstruction referred to NIOSH 

by the Department of Labor (DOL). As noted above, HHS will consider this determination to be 

sufficient without further consideration to determine that it is not feasible to estimate the levels of 

radiation doses of individual members of the class with sufficient accuracy. Although it is 

consequently not necessary for NIOSH to fully evaluate the feasibility of reconstructing external 

radiation exposures for the class of workers covered by this report, this sections presents NIOSH’s 
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findings regarding issues identified through the course of ongoing dose reconstruction and 

methodology reviews conducted by NIOSH and the Board after implementation of SEC-00064.

As presented above, the existing SEC class description for SEC-00064 was based on NIOSH’s 2006 

determination that exposure potential was limited to workers in specific buildings, that all workers 

with the potential for radiation exposures during the SEC-00064 class time period were included in 

the external dose monitoring program, and that unmonitored workers had no potential for radiation 

exposures. Through the course of ongoing dose reconstruction and methodology reviews conducted 

by NIOSH and the Board after implementation of SEC-00064, the following issues have been 

identified that may pertain to assessing external exposures during the General Atomics period from 

1960 through 1969:

• External photon and neutron angles of incidence associated with reconstructing beta doses for skin 

cancers

• The validation of neutron adjustment factors presented in the General Atomics Site Profile 

(ORAUT-TKBS-0045)

• The neutron energy distributions assumed

Due to thus far unresolved issues such as those indicated above, NIOSH has determined that 

infeasibilities associated with sufficiently accurate reconstruction of worker doses during the period 

from January 1, 1960 through December 31, 1969 extend beyond the assessment of internal 

exposures, as was presented in NIOSH’s 2006 evaluation of SEC-00064. NIOSH has determined that 

it is unable to define individual worker exposure scenarios for those workers that were not monitored 

for external exposure at General Atomics during the period 1960 through 1969. NIOSH has been 

unable to verify that external monitoring results are available for all workers with potential for 

external beta, gamma, or neutron exposures during the period.

NIOSH does not have access to sufficient personnel monitoring, workplace monitoring, or source 

term data to estimate unmonitored external beta, gamma, or neutron exposures during the period of 

AWE operations from January 1, 1960 through December 31, 1969. 

In addition, NIOSH considers the adequate reconstruction of medical dose for General Atomics 

workers feasible by using claimant-favorable assumptions as well as applicable protocols specified in 

the complex-wide TIB ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction 

from Occupationally Related Diagnostic X-Ray Procedures.

Although NIOSH found that it is not possible to completely reconstruct external radiation doses for 

the proposed class, NIOSH intends to use any external monitoring data that may become available for 

an individual claim (and that can be interpreted using existing NIOSH dose reconstruction processes 

or procedures). Therefore, dose reconstructions for individuals employed at General Atomics during 

the period from January 1, 1960 through December 31, 1969, but who do not qualify for inclusion in 

the SEC, may be performed using these data as appropriate.
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6.3 Class Parameters Associated with Infeasibility

HHS has designated an SEC class associated with SEC-00064 for General Atomics workers for the 

period from January 1, 1960 through December 31, 1969 (HHS, 2007). The time period covered by 

this current report is unchanged from that previously designated by HHS in 2007. The area-specific 

and personnel monitoring requirements designated by HHS in 2007 are removed by this current 

report. NIOSH therefore recommends that the current class include all workers and all areas of the

General Atomics site for the time period from January 1, 1960 through December 31, 1969.

7.0 Summary of Feasibility Findings for Petition SEC-00218

This report evaluates the feasibility for completing dose reconstructions for employees at General 

Atomics from January 1, 1960, through December 31, 1969. NIOSH determined that members of this 

class may have received radiation exposures from radionuclides of uranium, thorium, plutonium,

tritium, and fission and activation products associated with radiological research and production 

activities, including reactor and accelerator operations. NIOSH lacks sufficient information, including

biological monitoring data, sufficient air monitoring information, or sufficient process and 

radiological source information that would allow it to estimate with sufficient accuracy the potential 

unmonitored internal exposures, including unmonitored uranium, thorium, plutonium, tritium, and 

fission and activation products, to which the proposed class may have been subjected.

NIOSH has documented herein that it cannot complete the dose reconstruction(s) related to this 

petition. The basis of this finding demonstrates that NIOSH does not have access to sufficient 

information to estimate either the maximum radiation dose incurred by any member of the class or to 

estimate such radiation doses more precisely than a maximum dose estimate.

NIOSH has determined that it is necessary to remove the area-specific and monitoring criteria from 

the class description associated NIOSH’s 2006 evaluation of SEC-00064 exposures for the period 

from January 1, 1960 through December 31, 1969. Additionally, due to the issues identified during 

ongoing dose reconstruction and methodology reviews conducted by NIOSH and The board after 

implementation of SEC-00064, NIOSH has determined that infeasibilities associated with sufficiently 

accurate reconstruction of internal exposures during the period from January 1, 1960 through 

December 31, 1969 extend beyond the assessment of thorium exposures as was presented in NIOSH’s 

2006 evaluation of SEC-00064. NIOSH lacks sufficient information that would allow it to estimate 

with sufficient accuracy the potential unmonitored internal exposures, including unmonitored 

uranium, thorium, plutonium, tritium, and fission and activation products, to which the proposed class 

may have been subjected. 
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Table 7-1: Summary of Feasibility Findings for General Atomics

January 1, 1960 through December 31, 1969

Source of Exposure

SEC-00064 Previous Designation

SEC class effective March 18, 2007

SEC-00218 NIOSH Determination

Reconstruction 

Feasible

Reconstruction 

Not Feasible

Reconstruction 

Feasible

Reconstruction Not 

Feasible

Internal1

X X

- Thorium X X (unmonitored)1

- Thorium Progeny Not Specifically Addressed X (unmonitored)1

- Uranium

(Natural, Depleted and 

Enriched)

X

(October 1963 

onward)

X

(before October 

1963)

X (unmonitored)1

- Uranium Progeny Not Specifically Addressed X (unmonitored)1

- Plutonium Not Specifically Addressed X (unmonitored)1

- Tritium X

(October 1965 

onward)

X

(before October 

1963)

X (unmonitored)1

- Fission and 

Activation Products Not Specifically Addressed X (unmonitored)1

External X X

- Gamma X X (unmonitored)1

- Beta X X (unmonitored)1

- Neutron X X (unmonitored)1

- Occupational Medical 

X-ray

X X

Notes:

1 - Although NIOSH found that it is not possible to completely reconstruct radiation doses for the proposed class, NIOSH 

intends to use any internal and external monitoring data that may become available for an individual claim (and that can be 

interpreted using existing NIOSH dose reconstruction processes or procedures).

Through the course of ongoing dose reconstruction and methodology reviews conducted by NIOSH 

and the Board after implementation of SEC-00064, NIOSH has also determined that NIOSH is unable 

to define individual worker external exposure scenarios for those worker that were not monitored for 

external exposure. NIOSH does not have access to sufficient personnel monitoring, workplace 

monitoring, or source term data to estimate unmonitored external beta, gamma, or neutron exposures 

during the period of AWE operations from January 1, 1960 through December 31, 1969. NIOSH 

considers the adequate reconstruction of medical dose for General Atomics workers feasible by using 

claimant-favorable assumptions as well as applicable protocols specified in the complex-wide 

ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction from Occupationally 

Related Diagnostic X-Ray Procedures.

Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for individuals employed at 

General Atomics during the period from January 1, 1960 through December 31, 1969, but who do not 

qualify for inclusion in the SEC, may be performed using these data as appropriate.
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8.0 Evaluation of Health Endangerment for Petition SEC-00218

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by EEOICPA and 42 C.F.R. § 83.14(b) and § 83.13(c)(3). Pursuant to these requirements, if 

it is not feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH 

must determine that there is a reasonable likelihood that such radiation doses may have endangered 

the health of members of the class. The regulations require NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high-level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

NIOSH has determined that members of the class were not exposed to radiation during a discrete 

incident likely to have involved levels of exposure similarly high to those occurring during nuclear 

criticality incidents. However, the evidence reviewed in this evaluation indicates that some workers in 

the class may have accumulated chronic radiation exposures from uranium, thorium, plutonium, 

americium, tritium, and fission and activation products associated with radiological research and 

production activities, including reactor and accelerator operations. Consequently, NIOSH is 

specifying that health was endangered for those workers covered by this evaluation who were 

employed for a number of work days aggregating at least 250 work days within the parameters 

established for this class or in combination with work days within the parameters established for one 

or more other classes of employees in the SEC.

9.0 NIOSH-Proposed Class for Petition SEC-00218

The evaluation defines a single class of employees for which NIOSH cannot estimate radiation doses 

with sufficient accuracy. This class includes all Atomic Weapons Employees who worked for 

General Atomics at its facility in La Jolla, California, during the period from January 1, 1960 through 

December 31, 1969, for a number of work days aggregating at least 250 work days, occurring either 

solely under this employment or in combination with work days within the parameters established for 

one or more other classes of employees included in the Special Exposure Cohort.

10.0 Evaluation of Second Similar Class

In accordance with § 83.14(a), NIOSH may establish a second class of co-workers at the facility, 

similar to the class defined in Section 9.0, for whom NIOSH believes that dose reconstruction may not 

be feasible, and for whom additional research and analyses is required. If a second class is identified, 

it would require additional research and analyses. Such a class would be addressed in a separate SEC 

evaluation rather than delay consideration of the current claim. At this time, NIOSH has not identified 

a second similar class of employees at General Atomics for whom dose reconstruction may not be 

feasible.
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11.0 References

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, p 22,296; May 2, 2002; SRDB Ref ID: 19391

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001

42 U.S.C. §§ 7384-7385 [EEOICPA], Energy Employees Occupational Illness Compensation 

Program Act of 2000; as amended; DCAS website

Bethard, May1961, Highlights of the Medical Department from April 22, 1961 through May 22, 1961, 

correspondence to H. B Fry; W. F. Bethard; May 23, 1961; SRDB Ref ID: 20271, PDF pp. 59-63

Bethard, Jun1961, Highlights of the Medical Department from May 23, 1961 through June 22, 1961, 

correspondence to H. B Fry; W. F. Bethard; June 22, 1961; SRDB Ref ID: 20271, PDF pp. 64-73

Bethard, Sep1961, Highlights of the Medical Department from August 24, 1961 through September 

18, 1961, correspondence to H. B Fry; W. F. Bethard; September 18, 1961; SRDB Ref ID: 20271, 

PDF pp. 98-104

Bold, 1961, Progress Report for Period May 16, 1961 through June 15, 1961, correspondence to W. 

H. Ray; F. O. Bold; June 19, 1961; SRDB Ref ID: 20367, PDF pp. 130-131

Bold, 1962, Health Physics Operations Report for Period January 15, 1962 through February 15, 

1962, correspondence to W. F. Bethard; F. O. Bold; February 15, 1962; SRDB Ref ID: 20367, PDF p. 

121

Bold, 1963, Health Physics Report for the Period January 1, 1963 through January 31, 1963, 

correspondence to E. A. Long; F. O. Bold; February 12, 1963; SRDB Ref ID: 20367, PDF pp. 85-88

Bold, 1964, Health Physics Report for the Period October 1, 1964 through October 31, 1964, 

correspondence to E. A. Long; F. O. Bold; November 18, 1964; SRDB Ref ID: 20367, PDF pp. 9-12

Bold, 1968, Radiological Safety Guide, GGA-417 (Rev. 3/68); F. O. Bold; Rev. March 1968; SRDB 

Ref ID: 17859 

Cockle, 1965, October Monthly Report – TRIGA and Activation Analysis Facilities, correspondence to 

F. O. Bold; R. J. Cockle; November 1, 1965; SRDB Ref ID: 19000, PDF p. 109-113
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DCAS, 2010, DCAS Assessment Report-Review of SEC Class Definitions; Division of Compensation 

Analysis and Support (DCAS), Lara Hughes; November 3, 2010; SRDB Ref ID: 99551

General Atomics, 1960, Draft Safety Study for the General Atomic Hot Cell Facility; General Atomics 

Division of General Dynamics Corporation and Holmes & Narver, Inc.; December 21, 1960; SRDB 

Ref ID: 17538

General Atomics, 1961, Safety Study for the General Atomic Hot Cell Facility; General Atomics 

Division of General Dynamics Corporation and Holmes & Narver, Inc.; January 21, 1961; SRDB Ref 

ID: 17939 

General Atomics, 1964, A Report on General Atomics Division of General Dynamics; General 

Atomics Corporation; Fall 1964; SRDB Ref ID: 20410

General Atomics, 1966-1969, Instruction Manual for the Torrey Pines TRIGA Reactors, GA-7275; 

General Atomics; August 1, 1966 and then interim changes on October 15, 1968 and February 11, 

1969; SRDB Ref ID: 20366 

General Atomics, 1998, General Atomics Hot Cell Facility Decommissioning Plan, PC-000423/4; 

General Atomics Corporation; January 1998; SRDB Ref ID: 18096 

Gurren, 1966, Hand Exposure of [Redacted] at Triga Facility -7-01-1966, correspondence to F. O. 

Bold; E. J. Gurren; July 5, 1966; SRDB Ref ID: 17917, PDF p. 31

Helgeson, 1966, Report of Whole Body Counting for General Atomics; Helgeson Nuclear Services;

May 3, 1966; SRDB Ref ID: 19024 

Helgeson, 1969, Report of In Vivo Counting for Gulf General Atomics, Work Performed on May 26-

29, 1969; Helgeson Nuclear Services Pleasanton; Report dated September 19, 1969; SRDB Ref ID: 

20403 

HHS, 2007, HHS Designation of Additional Members of the Special Exposure Cohort under the 

Energy Employees Occupational Illness Compensation Program Act for General Atomics, La Jolla, 

California; Health and Human Services (HHS); February 16, 2007; SRDB Ref ID: 56081

Hughes, 1964, Urine Bioassays of [Redacted], correspondence to F. O. Bold; G. J. Hughes; March 20, 

1964; SRDB Ref ID: 17928 

Hughes, 1967, Report of Fire in Controlled Area on 12-28-66, correspondence to F. O. Bold; G. J. 

Hughes; January 3, 1967; SRDB Ref ID: 17914 

Hughes, 1969, Contamination in Clean High Bay, correspondence to F. O. Bold; G. J. Hughes;

January 24, 1969; SRDB Ref ID: 17975 

Kesting, 1964, High Radiation Field in LINAC Flight Path Area, correspondence to F. O. Bold; H. L. 

Kesting and R. J. Cockle; January 30, 1964; SRDB Ref ID: 17889, PDF pp. 5-6

Kesting, 1969, Contamination Incident in Lab L-218, correspondence to F. O. Bold; H. L. Kesting;
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January 29, 1969; SRDB Ref ID: 17974, PDF pp. 13-14

Lepper, 1963, Radioactive Spill in L-403, correspondence to F. O. Bold; F. R. Lepper; September 19, 

1963; SRDB Ref ID: 17890

NIOSH, 2006, SEC Petition Evaluation Report for Petition SEC-00064, General Atomics; National 

Institute for Occupational Safety and Health (NIOSH); September 20, 2006; SRDB Ref ID: 133364

ORAUT-OTIB-0006, Dose Reconstruction from Occupationally-Related Diagnostic X-Ray 

Procedures, Rev. 04; ORAU Team Dose Reconstruction Project for NIOSH; June 20, 2011; SRDB 

Ref ID: 98147

ORAUT-TKBS-0045, Site Profile for General Atomics, Rev. 00; ORAU Team Dose Reconstruction 

Project for NIOSH; effective September 26, 2008; SRDB Ref ID: 49950

Pound, 1974, TCF/ECF Facility, correspondence to C. J. Good; D. C. Pound; March 29, 1974; SRDB 

Ref ID: 20355, PDF pp. 2-4

Ray, 1960, Log Book Entry for Room L-540; signed by W. H. Ray; December 19, 1960; SRDB Ref 

ID: 17534, PDF p. 2

Russell, 1967, Thermionic Critical Experiment Spectrum Measurements: Description and Safety 

Analysis, J. L. Russell; September 8, 1967; SRDB Ref ID: 20353 

SNM-69, Special Nuclear Materials License 69 (Docket 70-72), with Amendments 1 through 62; 

General Atomics; La Jolla, California; March 29, 1963 and amendments with multiple dates; SRDB 

Ref ID: 19011, 19012, and 19013

SNM-696, Special Nuclear Materials License 696 (Docket 70-734); multiple dates; General Atomics; 

La Jolla, California; SRDB Ref ID: 19014
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Attachment One: Data Capture Synopsis

Table A1-1: Summary of Holdings in the SRDB for General Atomics, La Jolla, California

Data Capture Information Data Capture Description Date 

Completed

Uploaded 

into SRDB

Primary Site/Company Name: General 

Atomics

BE 1959-1967; AWE 1960-1969; Residual 

Radiation 1970-1995, 2000; DOE 1996-1999 

(Remediation) 

Other Site Names:

GA

Division of General Dynamics

John Jay Hopkins Laboratory for Pure and 

Applied Science

Physical Size of the Site: 

General Atomics occupies approximately 120 

acres on two contiguous sites. The Hot Cell 

Facility encompassed approximately 7,400 

square feet. The site contained 43 buildings in 

1994.

Site Population:

Samples of the number of personnel monitored 

for radiation exposure (excluding visitors) 

during the SEC064 period of 1/1/1960 -

12/31/1969 based on monthly exposure 

printouts are: 350 (April 1960); 390 (December 

1964). Note: for additional informational 

purposes only, there were 1400 total personnel 

on site in 1994.

Decontamination and decommissioning of hot cell proposal, personnel list, 

bioassay data, personnel termination reports, isotope committee approvals, 

environmental data, personnel radiation exposure, uranium scrap recovery 

operations, radiological surveys, site, facility, fuel material and waste 

characterization plan, safety evaluation report, air sample data, license 

SNM-69 material, hot cell area dosimeter readings, investigation reports, 

radiological safety guide and procedures, emergency plan, hot cell facility 

reports, incident reports, hot cell facility procedures, byproduct material, 

license 4-1611-11, decommissioning and decontamination of fuel 

fabrication facility, trip reports, health physics reports, determination of fast 

and thermal neutron dosages, license manuals, material balance reports, 

whole body counts, in-vivo lung and total body counter, and General 

Atomics notebooks.

Note: Additional data capture not required per NIOSH direction.

03/22/2011 416

State Contacted: NA Note: Additional data capture not required per NIOSH direction. 03/22/2011 0

Battelle National Laboratory - King Avenue A hazard report. 04/11/2011 1

DOE Carlsbad HTGR applications program contract summary and safety analysis 

supplement for the standard MHTGR.

08/10/2010 2

DOE Germantown Contract AT(40-1)-3367-General Atomics, U-233 product distribution, and 

Westinghouse Hanford Company audit of Gulf General Atomic, toxic 

06/18/2008 10
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Table A1-1: Summary of Holdings in the SRDB for General Atomics, La Jolla, California

Data Capture Information Data Capture Description Date 

Completed

Uploaded 

into SRDB

hazards of beryllium.

DOE Legacy Management - Grand Junction 

Office

Long range plan for fiscal years 1985-1988, termination dosimetry reports, 

thorium stockpile and use in breeder reactor, trip reports, National Lead 

Company of Ohio minutes of staff meeting, bills of lading for shipments, 

shipping logs, disposition of enriched uranium scrap, thorium sludge 

shipments, summary of Brazilian thorium sludge transferred to NLO, and 

purchasing of DOE thorium residues.

09/20/2010 28

DOE Legacy Management - Morgantown Enriched uranium shipment information. 02/03/2011 2

DOE Legacy Management - MoundView Bioassay information, radioactive waste management report, and a 

Building 21 acceptance document.

09/08/2008 9

DOE Office of Scientific and Technical 

Information (OSTI)

Hot cell final environmental assessment, survey of irradiation facilities, and 

a verification survey of the hot cell, breeder fuel development program 

report, and radioactive waste shipment information.

11/05/2012 10

DOE Oak Ridge Operations (ORO) Personnel exposure records, future use and disposition of uranium-233, and 

special nuclear material inventory.

07/09/2012 3

Federal Records Center (FRC) - San Bruno Analysis of nuclear radiation shields, photo induced reactions to nuclear 

safeguards materials, curium-224/neptunium-237 recovery from the 

Barnwell Nuclear Fuel Plant, monthly progress report, procedure manuals, 

utilization of neutron radiography, SNAP program cost and schedule report, 

fabrication of a thermionic reactor system using U-233, fast neutron 

weighting factors, summaries of fuels and materials development programs, 

and thorium utilization program information.

08/03/2012 19

Hanford History of Fernald thorium process operations and monthly reports. 11/24/2008 5

Idaho National Laboratory Lung and thyroid counter calibration information. 05/09/2012 1

Internet - Defense Technical Information 

Center (DTIC)

Shielding and control materials for gas cooled fast breeder reactor, 

displacement radiation effects report, and a progress report.

12/05/2012 4

Internet - DOE Hanford Declassified Document 

Retrieval System (DDRS)

Hanford operations monthly reports. 01/14/2008 5

Internet - DOE Legacy Management 

Considered Sites

Radiological survey data, hot cell decommissioning plan, and fuel material 

characterization and packing report, and a management guide.

08/01/2012 8

Internet - DOE OpenNet Linking Legacies Appendix B and a financial report. 09/20/2012 5

Internet - DOE OSTI Energy Citations Program summary, thorium use progress report, and processing of Pu-238. 03/28/2013 5

Internet - DOE OSTI Information Bridge Report on shipments to and from the Nevada Test Site and counting 

laboratory intercalibration information, site treatment plan, emergency 

preparedness source term information, user facilities at the Lawrence 

Berkeley National Laboratory, and fission product tritium distribution in 

zircaloy cladding.

03/29/2013 22
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Table A1-1: Summary of Holdings in the SRDB for General Atomics, La Jolla, California

Data Capture Information Data Capture Description Date 

Completed

Uploaded 

into SRDB

Internet - Google Annual report to Congress of the Atomic Energy Commission, hot cell 

characterization, decontamination and decommissioning, information on 

nuclear batteries, and the importance of gas cooled reactors.

04/14/2013 37

Internet - NIOSH A beryllium contamination report. 09/14/2011 5

Internet - NRC Agencywide Document Access 

and Management (ADAMS)

FUSRAP sites review, NUREG-0713 excerpts, and NRC decommissioning 

criteria.

03/26/2013 26

Internet - Oak Ridge National Laboratory 

(ORNL)

Progress and status reports and out of pile studies of fission product release. 12/18/2012 19

Kansas City Plant Radioactive sources documentation. 12/04/2012 1

National Archives and Records Administration 

(NARA) - Atlanta

Information on the Dragon Project, feasibility report for the General 

Atomic HTGR critical assembly fuel elements, and documentation 

regarding U-233 thorium project.

05/20/2008 4

National Archives and Records Administration 

(NARA) - College Park

Survey of a beryllium problem. 09/11/2002 1

National Institute for Occupational Safety and 

Health (NIOSH)

Establishment of compensation program. 12/12/2011 1

Nevada Test Site (NTS) Final environmental impact statement for the Nevada Test Site. 10/01/2003 1

Nuclear Regulatory Commission PDR Semi annual effluent report. 06/06/2011 2

Oak Ridge National Laboratory (ORNL) Radioisotope sales and a progress report. 01/23/2013 2

ORAU Team Documented communication and technical basis documents. 03/06/2012 4

R. S. Landauer No relevant documents identified. 07/07/2014 0

SAIC Radiation exposure summary. 09/02/2004 5

S. Cohen & Associates (SC&A) Fernald related radioactive material information and license documents. 04/07/2011 4

Sandia National Laboratory - NM A trip report. 07/10/2005 1

Savannah River Site Visitor dosimetry cards, thoria fuel irradiation program information, and 

progress reports.

03/19/2012 11

Southern Illinois University, Edwardsville, IL Environmental and health legacy of the Mallinckrodt Chemical Works. 10/29/2008 2

Unknown Final safety analysis report, personnel external exposure information, 

reports on nuclear reactor program and special nuclear material license No. 

SNM-33.

07/31/2003 10

Westinghouse Site Employee exposure records. 04/07/2009 1

Total 692
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Table A1-2: Database Searches for General Atomics, La Jolla, California

Database/Source Keywords Hits Uploaded 

into SRDB

Note: The normal prescribed publicly accessible Internet database searches are currently in progress for General Atomics.

Table A1-3: OSTI Documents Requested for General Atomics, La Jolla, California

Document Number Document Title Requested 

Date

Received 

Date

GA-A-15793

Ref ID: 111592

Consolidated fuel reprocessing program. Quarterly progress report for the 

period ending February 29, 1980

11/22/2011 06/01/2012